<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>天气案例_深度监视</title>
    <script src="../js/vue.js"></script>
</head>

<body>
    <div id="root">
        <h2>今天天气很{{info}}</h2>
        <!-- <button @click="isHot=!isHot">切换天气</button> -->
        <button @click="changeWeather">切换天气</button>
    <hr>
        <h3>a的值是{{numbers.a}}</h3>
        <button @click="numbers.a++">点我让a+1</button>
    <hr>
        <h3>b的值是{{numbers.b}}</h3>
        <button @click="numbers.b++">点我让b+1</button>
        <button @click="numbers={a:666,b:888}">彻底替换掉numbers</button>
    </div>
</body>
<script>
    Vue.config.productionTip = false
    const vm=new Vue({
        el: '#root',
        data: {
            isHot: true,
            numbers:{
                a:1,
                b:1
            }
        },

        computed: {
            info(){
                return this.isHot ? '炎热' : '寒冷'
            }
        },
        methods: {
            changeWeather() {
                this.isHot = !this.isHot
            }
        },
        watch:{
            isHot:{
            // 'numbers.a':{
            //      handler(){
            //         console.log('a被修改了');
            //     }
            // }
               numbers:{
                   deep:true,//监视多级结构中某个属性的变化
                   handler(){
                       console.log('number被修改了');
                   }
               }
            }
        }

    })
    // vm.$watch('isHot',{
    //     immediate:true,//初始化时，让handler调用一下
    //     // isHot什么时候调用？当isHot发生改变时
    //     handler(newValue,oldValue){
    //         console.log('isHot被修改了',newValue,oldValue);
    //     }
    // })
</script>

</html>